Polyvinyl alcohol alloys and method of making the same

ABSTRACT

A polyvinyl alcohol alloy useful as a gas barrier material is prepared by reacting polyvinyl alcohol and a functional polymer to provide a product which has low gas permeability and water absorptivity characteristics, and which has a melting point sufficiently below its decomposition point to allow melt extrusion. The alloy may optionally be mixed with a polyolefin blending resin.

CROSS-REFERENCE TO RELATED APPLICATION

This is a division of co-pending, commonly assigned application Ser. No.578,111 filed Feb. 8, 1984, now U.S. Pat. No. 4,575,532.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to polyvinyl alcohol alloys which havedesirable physical characteristics including low gas permeability, lowmoisture absorptivity, and relatively low melting points.

2. Description of the Prior Art

Polyvinyl alcohol (PVA) has the lowest gas permeability of any polymeryet synthesized, and has found widespread application as a gas barriermaterial, especially as an oxygen barrier material. Commercial polyvinylalcohols have several failings, however. Due at least in part to theirhigh polarity, their melting points are close to their decompositionpoints and, thus, they are not melt extrudable. Most films are cast fromwater or use large percentages of a polyhydric alcohol or polyethyleneoxide (with or without added water) to plasticize the melt so thatextrusion can be effected. Prior PVA polymers absorb relatively largequantities of moisture. The presence of moisture in turn raises theoxygen permeability of the polymers drastically.

One approach known in the art to alleviate these difficulties has beento introduce hydrocarbon units, especially ethylene units, into thechain of the polymer. The resulting materials are known as ethylenevinylalcohol (EVOH) copolymers. EVOH copolymers have been used verysuccessfully in a number of commercial applications, but are quiteexpensive. In addition, close control of composition and elimination ofhomopolymer by-products are required in the production of EVOHcopolymers. A broad distribution of ethylene results in poor water vaportransmission rate properties. The presence of homopolymer leads to atendency to develop gel specks and/or burn spots during the extrusionprocess.

SUMMARY OF THE INVENTION

The present invention is directed to overcoming one or more of theproblems described above by providing a polyvinyl alcohol materialhaving excellent gas barrier characteristics without high sensitivity towater.

According to the present invention, a novel polyvinyl alcohol alloy thatis relatively inexpensive, has a melting point below its decompositionpoint so as to allow melt extrusion, and has reduced moisture absorptioncharacteristics, and a method of making such an alloy, are provided.

The inventive method comprises the step of reacting polyvinyl alcoholwhich is less than about 98 mole percent hydrolyzed with less than astoichiometric amount of a functional polymer which is a polyolefinincorporating reactive functional groups, to produce a mixture ofgrafted and ungrafted polyvinyl alcohol. The functional groups may begrafted to the polyolefin or incorporated into the polyolefin chain.

The mixture of grafted and ungrafted polyvinyl alcohol can optionally bemelt blended with a compatible polyolefin blending resin to produce analloy having desired gas barrier, low water vapor transmission, lowwater sensitivity, and processability characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a Fourier Transform Infrared (FTIR) spectrum of a polyvinylalcohol which is 87 mole percent hydrolyzed and which has a 4% aqueoussolution viscosity of about 5 cps at 20° C.;

FIG. 2 is an FTIR spectrum of a graft copolymer comprising apolyethylene backbone grafted with x-methylbicyclo(2.2.1)hept-5-ene-2,3-dicarboxylic anhydride (XMNA);

FIG. 3 is an FTIR spectrum of a reaction product of the compounds ofFIGS. 1 and 2; and,

FIG. 4 is an FTIR spectrum representing the subtraction of the spectraof FIGS. 1 and 2 from that of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION General Description

Polyvinyl alcohol (PVA) polymers and copolymers are highly polar; andthe high hydroxyl content of such polymers render them effective as gasbarrier materials. Unfortunately, however, this high hydroxyl contentresults in very high moisture sensitivity of these materials.

By the method of the invention, desirable moisture resistancecharacteristics attributable to hydrocarbons are introduced into PVApolymers while retaining the desirable gas barrier characteristicsassociated with high hydroxyl content.

This is accomplished by providing a physical mixture of grafted andungrafted PVA and, optionally, melt blending this mixture with acompatible olefin homopolymer or copolymer blending resin.

The mixture of grafted and ungrafted PVA is produced by reacting aquantity of ungrafted PVA with an olefin polymer having functionalgroups reactive with the hydroxyl groups of the PVA. The backbone of thefunctional polymer is an olefin homopolymer or copolymer, and themonomer containing functional groups may comprise part of the backboneor be present as side chains. The amount of the functional polymer isselected such that substantially less than all the available hydroxylgroups on any given PVA chain are reacted, and such that a substantialproportion of the available PVA chains remain ungrafted.

If too high a proportion of available hydroxyl groups are reacted, themixture will be rendered unprocessable, due to an extreme rise inviscosity and a decrease in melt index (MI) resulting from cross-linkingand gelling of the PVA.

It has been found that such limited grafting of PVA to provide aphysical mixture of grafted and ungrafted PVA results in an alloymaterial exhibiting excellent moisture resistance and good separation ofthe melting and decomposition points, without a significant loss of gasbarrier properties.

Melt blending of the mixture of grafted and ungrafted PVA with acompatible polyolefin blending resin results in the addition ofincreased hydrocarbon characteristics to the blend, thus increasingmoisture resistance, while retaining desirable processabilitycharacteristics.

The Polyvinyl Alcohol Polymer

Polyvinyl alcohol polymers suitable for use in this invention arepolyvinyl alcohol homopolymers or copolymers having a degree ofhydrolysis of less than about 98 mole percent. (PVA polymers having adegree of hydrolysis greater than about 98 mole percent result inproducts having melting points sufficiently close to their decompositionpoints that melt processing is unfeasible.) Preferably, the PVA shouldbe between 70 and 90 mole percent hydrolyzed and have a degree ofpolymerization (DP) of between about 300 and 900. Other PVA polymers,however, are also suitable.

The Functional Polymer

Suitable functional polymers comprise any polyolefins which incorporatefunctional groups reactive with the hydroxyl groups of the PVA. Suitablefunctional groups include carboxylic acids, carboxylic acid anhydrides,metal salts of a carboxylic acid, derivatives thereof, or mixtures.Suitable examples are graft copolymers based on an olefin homopolymer orcopolymer backbone. Particular polyolefins suitable for use as graftcopolymer backbones in this invention include polyethylene, ethylenecopolymers, polypropylene, and propylene copolymers.

Other copolymers useful as graft copolymer backbones includeolefin-ester copolymers such as ethylene-vinyl acetate, otherethylene-vinyl esters, ethylene-acrylate esters andethylene-methacrylate ester copolymers.

Specific examples of suitable functional polymers include polyethyleneand polypropylene homopolymers or copolymers grafted with maleicanhydride, ethylene-acrylic acid or ethylene-methacrylic acid randomcopolymers or ethylene-acrylic acid or ethylene-methacrylic acidionomers, and ethylene-propylene rubbers grafted with fumaric acid.

Any unsaturated carboxylic acid or carboxylic acid anhydride can be usedto form polyolefin graft copolymers suitable for use in this invention.Some of these are maleic anhydride, x-methylbicyclo(2.2.1)-hept-5-ene-2,3-dicarboxylic anhydride (XMNA),bicyclo(2.2.1)hept-5-ene-2,3-dicarboxylic anhydride, citraconicanhydride, itaconic anhydride, and 1,4-butenedioic acid monoalkylesters. Dicarboxylic acids, monoester acid derivatives, or maleamicacids which can form these anhydrides or anhydride derivatives can alsobe used.

The carboxylic acid, anhydride, metal salt or other carboxylic acidderivative need not be grafted onto the polyolefin backbone of thefunctional polymer, but may be incorporated into the chain bycopolymerization. Examples of copolymers suitable for use as acidfunctional polymers are ethylene-acrylic acid, ethylenemethacrylic acid,ethylene-alkyl acrylate-acrylic acid copolymers or ethylene-alkylmethacrylate-methacrylic acid copolymers and their partially neutralizedsalts (known as ionomers). Other useful copolymers are ethylene-vinylacetate-maleic anhydride, ethylene-methylacrylate-maleic anhydride,ethylene-methylmethacrylatemaleic anhydride, ethylene-maleic anhydride,ethylenemonoester of maleic acid, ethylene-vinyl acetate-1,4-butenedioicacid and its monoester, ethylene-alkyl acrylate-1,4-butenedioic acid andits monoester copolymers, and many other olefin combinations containingacid functionality like the partially neutralized metal salt derivativesof these copolymers and maleamic acid derivatives.

The Blending Resin

The blending resin is an olefin homopolymer or copolymer which iscompatible with the mixture of grafted and ungrafted PVA. Suitableblending resin polymers include, but are not limited to, high-, low- andmedium density polyethylene, propylene homopolymers and copolymers ofpropylene and ethylene, including block and random ethylene-propylenecopolymers and ethylene-propylene elastomers, and copolymers of ethylenewith olefins such as hexene-1, octene-1 and butene-1, including thosecopolymers known as linear low density polyethylene, for example.

The Nature of the Alloy and Proportions of Constituents

Fourier Transform Infrared (FTIR) spectral analysis of typical alloysand alloy-forming reactants of the invention shows the disappearance ofanhydride and the appearance of a new ester in the alloy at about 1225cm⁻¹ to 1230 cm⁻¹. This new ester can be distinguished from the acetateester resulting from unhydrolyzed acetate in the polyvinyl acetatehomopolymers or copolymers from which the polyvinyl alcohols areprepared (see FIGS. 1-4). This demonstrates that a new material isformed, and that this material is a reaction product (i.e. a graftcopolymer between the PVA and the functional polymer) as opposed to amere physical association between the PVA and copolymer.

The functional level of the functional polymer is defined by the amountof carboxylic acid, anhydride, metal salt or derivative containedtherein. If the functional level is too low, the reaction product willnot give a useful alloy when blended with the polyolefin polymer. On theother hand, if the functional group level is too high, the viscosity ofthe blended product becomes so high as to hinder its practicalprocessability. We do not wish to be held to this theory, but onepossible reason for decreased flow characteristics could be chainextension and/or cross linking of the PVA by reaction with thefunctional polymer.

The PVA-functional polymer reaction product acts as a compatibilizer toallow optional incorporation of a polyolefin blending resin into thereaction product to form other useful alloys. The presence of unreactedpolyolefin blending resin as part of a physical mixture with the PVAalloy allows one to select the proportion of added blending resin andthus balance moisture resistance and gas barrier properties as desired.Without the polyolefin-grafted PVA, the addition of a polyolefin to amelt blend would result in macrophase separation, as demonstrated in theExamples, below.

In the alloys of the invention, microphases may exist without observablemacrophase separation. As a result, the alloys may exhibit theappearance and behavior of single phase, homogeneous polymer blends.

The proportion of grafted PVA to ungrafted PVA, and the proportion ofpolyolefin blending resin to the mixture of grafted and ungrafted PVA,can be readily empirically determined by one skilled in the art. Ingeneral, the proportion of functional polymer in the alloy is selectedto provide both a desired level of moisture resistance and desired gasbarrier properties. The proportion of functional polymer should besufficient to separate the melting and decomposition points of the alloyso as to allow melt processing, yet insufficient to result in gelling.

For example, if the functional polymer is an HDPE homopolymer graftedwith 1.5 wt. % XMNA, the alloy should comprise at least about 70 wt. %PVA, in order to obtain a processable alloy and desired gas barrierproperties.

If present, the compatible blending resin can comprise between about 1and 15 wt. % of the alloy. The upper limit of the blending resinproportion is dictated by (1) desired gas barrier characteristics andwater resistance properties and (2) the amount of functional polymer inthe PVA mixture. This can be readily empirically determined, and the useof too high a proportion of blending resin results in observablemacrophase separation, as shown in the Examples, below.

The foregoing specific values are based on the use of HDPE homopolymergrafted with 1.5 wt. % of XMNA as the functional polymer. It will beappreciated that the properties of the alloy and the proportions ofconstituents vary with the choice of functional groups, functionalpolymer backbone, polyolefin blending resin, the hydroxyl content of thePVA polymer, and the molecular weight and melt index of each of the PVApolymer and the functional polymer.

Moisture pickup measurements show that the functional polymerhydrocarbon chains lower the moisture pickup of the alloys (see Table IIbelow). Since oxygen permeability is affected by the amount of moistureabsorbed, these alloys will have reduced oxygen permeability under highmoisture conditions. Oxygen permeability measurements on dry PVA alloysshow that they have excellent barrier properties against oxygen. Thealloys have impermeability at least 100 times better than Mylar® resins(oriented polyethylene terephthalate), and nylon 6, which haveheretofore been used in some barrier structures.

Gas barrier films, sheets, tubings, coatings, bottles, profiles, etc.can be formed from these alloys by blown and cast extrusion, extrusioncoating, coextrusion, coextrusion coating, injection molding, blowmolding, rotomolding, compression molding, profile, pipe and tubingextrusion or a combination of these processes. These articles can befabricated into pouches, bottles, pipe, tubing and other fabricatedarticles. Other shapes, articles and methods of fabrication forthermoplastics, blends and alloys obvious to one skilled in the art arealso included.

EXAMPLES

The following specific examples are intended to illustrate theinvention, but the scope of the invention is not to be considered to belimited thereby.

EXAMPLE 1

(a) 50 wt. % PVA (DP=330, 35 mole % hydrolyzed) and 50 wt. % HDPE graftcopolymer (graft monomer=XMNA, 1.5 wt. % incorporated, MI=1.5 g/10 min.)were reacted in a Brabender mixer at 325° F. (163° C.) for 5 min. at 120rpm. The reaction product, through use of FTIR spectral subtraction,shows the presence of bands at 1750 cm⁻¹ (carbonyl) and 1225 cm⁻¹(carbon-oxygen) which can be related to an ester other than acetate.

(b) 80 wt. % PVA (87 mole % hydrolyzed, 4% aqueous solution viscosity at20° C. of 5 cps) and 20 wt. % of the graft copolymer described in parta) above were blended in a Brabender mixer at 425° F. (218° C.) for 5minutes at 120 rpm. The reaction product, through use of FTIR spectralsubtraction, shows the presence of a band at 1229 cm⁻¹ (carbon-oxygen)which can be related to an ester other than acetate (see FIGS. 1-4).

EXAMPLE 2

30 wt. % PVA (DP=700, 74 mole % hydrolyzed) and 5 wt. % of the graftcopolymer as described in Example 1 were reacted in the presence of 65wt. % of an ethylene-butene-1 copolymer (MI=2, density=0.918 g/cc). Theamount of anhydride found by FTIR is 0.014 wt. %. The amount ofanhydride which would be present if no reaction occurred is 0.065 wt. %.

EXAMPLE 3

Alloys with the compositions listed in Table I, below, based on PVA "A"(87 mole % hydrolyzed, M_(w) =10,000, 4% aqueous solution viscosity of 5cps), PVA "B" (74 mole % hydrolyzed, DP=600), and the graft copolymerdescribed in Example 1, were submitted for FTIR analysis as described inExample 2. The results show that most of the anhydride of the graftcopolymer has disappeared. The theoretical percent of anhydride in TableI shows the amount which would be present if no reaction occurred.

                  TABLE I                                                         ______________________________________                                        Example 3                                                                     Polyolefin                                                                    Graft                   Anhydride                                             PVA "A" Copolymer PVA"B"    Observed Theoretical                              %       %         %         %        %                                        ______________________________________                                        --      20        80        0.06     0.28                                     --      40        60        0.13     0.56                                     80      40        --        0.03     0.56                                     60      20        --        0        0.28                                     ______________________________________                                    

EXAMPLE 4

70-95 wt. % of the PVA and correspondingly 30-5 wt. % of the polyolefingraft copolymer used in Example 1, 5000 ppm of Irganox 1010 (tetrakis[methylene(3,5-di-tert-butyl-4-hydroxyphenyl propionate)]methane fromCiba-Geigy) and 500 ppm of calcium stearate were reacted in an intensivemixer, using a steam heated rotor, for a period of 4-5 minutes. Thematerial was reacted at 430°-450° F. (221°-232° C.).

The reaction products obtained were extruded into films of variousthicknesses by use of a single screw extruder with a temperature profileof:

Zone 1=365°-380° F. (185°-193° C.)

Zone 2=405°-440° F. (207°-227° C.)

Zone 3=400°-440° F. (204°-232° C.)

Reaction products from 80 wt. % PVA and 20 wt. % of a polyolefin graftcopolymer (prepared by grafting XMNA onto HDPE) were extruded into 3 milfilm. These along with those made from 100% PVA "A" and "B",respectively, were dried in a vacuum oven to constant weight. They werethen placed in desiccators in which the atmosphere was controlled at 50%and 79.5% relative humidity, respectively. The films were weighed afterremaining in these atmospheres for eight days. The percent weight gainsare shown in Table II, below.

                  TABLE II                                                        ______________________________________                                        Example 4                                                                     PERCENT MOISTURE GAIN.sup.1 4                                                                  Relative Humidity                                                             50%   79.5%                                                  ______________________________________                                        PVA "A".sup.2      8.7     14.7                                               Reaction Product "A".sup.5                                                                       5.0      9.9                                               Reaction Product "C".sup.6                                                                       4.4     10.5                                               PVA "B".sup.3      4.7     10.0                                               Reaction Product "B".sup.5                                                                       3.5      8.3                                               ______________________________________                                         Notes:                                                                        .sup.1 3 mil film, weight gain after 8 days under the specified               conditions.                                                                   .sup.2 PVA "A" is 87 mole % hydrolyzed, M.sub.w = 10,000; 4% aqueous          solution viscosity at 20° C. of 5 cps.                                 .sup.3 PVA "B" is 74 mole % hydrolyzed, DP = 600.                             .sup.4 The graft copolymer used to prepare the reaction products contains     1.5 weight percent xmethyl bicyclo (2.2.1)hept 5ene-2,3-dicarboxylic          anhydride (XMNA) and has a melt index of 1.5 g/10 min. The backbone           polymer which is grafted has the foll owing properties: density = 0.96        g/cc and high load melt index = 3 g/10 min.                                   .sup.5 The reaction products contain 80% of the corresponding PVA and 20%     of the graft copolymer.                                                       .sup.6 Reaction product "C" contains 80% of PVA "A", 10% of a linear low      density polyethylene (LLDPE) composed of ethylene and butene1 which has a     density of 0.918 g/cc and a melt index (MI) of 2 g/10 min and 10 wt. % of     the graft copo lymer described in note 4, above.                         

EXAMPLE 5

PVA/functional polymer reaction products were also made using the PVApolymers listed below.

                  TABLE III                                                       ______________________________________                                        Example 5                                                                                       Mole %                                                      DP.sup.1                                                                              Visc..sup.2                                                                             Hydrolyzed                                                                              M.sub.n    M.sub.w                                ______________________________________                                        500-700.sup.                                                                          4-6       87.0-89.0 22,000-31,000                                                                            --                                     1750-1800.sup.3                                                                       28-32     99.7+     --         --                                     500-700.sup.3                                                                         5-7       98.0-98.8 22,000-31,000                                                                            --                                             4-6       88.7-85.5 --         10,000                                         2.4-3       77-72.9 --          3,000                                         1.8-2.4     77-72.9 --          2,000                                 850     --        73        --         --                                     700     --        73        --         --                                     600     --        74        --         --                                     650     --        37        --         --                                     330     --        35        --         --                                     ______________________________________                                         Notes:                                                                        .sup.1 Degree of polymerization.                                              .sup.2 Viscosity (in centipoise) of a 4% aqueous solution at 20° C     .sup.3 Thermal decomposition occurs.                                     

The results shown in Table III demonstrate that PVA polymers having adegree of hydrolysis greater than about 98 mole percent do not formuseful alloys according to the present invention.

Other anhydride-containing functional polymers which were studiedinclude:

1. A graft of XMNA onto an ethylene-butene-1 copolymer (linear lowdensity PE with a high load melt index (HLMI) of 2.6 g/10 min anddensity=0.917 g/cc), content of XMNA=1.4 wt. %, MI=1 for the graftcopolymer.

2. An EVA containing 14% vinyl acetate and 0.29% of maleic anhydride anda melt index (MI)=6-8.

3. A graft of XMNA onto an EVA containing 28% vinyl acetate, MI=6.Content of XMNA=0.87 wt. % and MI of graft copolymer=1.2.

4. A graft of maleic anhydride (MA) onto HDPE. Content of MA is 1.02 wt.%.

EXAMPLE 6

This example shows the decrease in melt flow rate (MFR) found when theproportion of functional polymer in the reaction product is increased.

A reaction of the polyolefin graft copolymer described in Example 1 withmodified PVA, as described in Table IV, below, is performed at 425° F.(218° C.) for 5 min. in an electrically heated scroll mixer (e.g. aBrabender mixer). The melt flow rates (MFR) are taken at 230° C. using a2160 g weight as described in ASTM 1238 (Condition L).

                  TABLE IV                                                        ______________________________________                                        Example 6                                                                     Effect of Functional Polymer Concentration On Processibility.sup.3                        Polyolefin Graft                                                              Copolymer.sup.2                                                               %          MFR.sup.4                                              ______________________________________                                        PVA "A".sup.1 %                                                               100           --            21.4                                              95             5            19.3                                              80            20            5.3                                               70            30            0.65                                              60            40            0.12                                              PVA "B".sup.1 %                                                               100           --            9.8                                               90            10            4.6                                               85            15            2.4                                               80            20            1.3                                               70            30            0.2                                               60            40            0.0                                               ______________________________________                                         Notes:                                                                        .sup.1 PVA "A" and "B" as in Example 3.                                       .sup.2 Graft copolymer as in Example 3.                                       .sup.3 All samples reacted at 425° F. for 5 min.                       .sup.4 ASTM 1238 (Condition L)  230° C., 2160 g.                  

EXAMPLE 7 (COMPARATIVE)

Varying percentages of non-grafted PVA, as designated in Table V, below,and an ethylene-butene-1 copolymer (linear low densitypolyethylene-LLDPE) with an MI of 2 g/10 min. and a density of 0.918g/cc were blended in an electrically heated scroll mixer at 425° F.(218° C.) for 5 min. at 120 rpm. Gross macrophase separation wasobserved in which the macrophases were different in color and behavior.The smaller macrophase is indicated as percent separated in Table V,below. These data show that the blends of PVA with LLDPE are notmacroscopically homogeneous.

                  TABLE V                                                         ______________________________________                                        Example 7                                                                     PVA "A"    PVA "B"   LLDPE       Separation                                   %          %         %           %                                            ______________________________________                                        95          0         5          1.8                                          90          0        10          3.6                                          85          0        15          8.0                                          70          0        30          15.0                                          0         95         5          2.1                                           0         90        10          5.0                                           0         85        15          7.0                                           0         70        30          13.8                                         ______________________________________                                    

EXAMPLE 8

A number of reaction products were prepared using 20 wt. % of thepolyolefin graft copolymer used in Example 1 combined with variousamounts of the LLDPE described in Example 7, and PVA "A" as described inExample 4. The results are shown in Table VI, below. No macrophaseseparation occurs. This demonstrates the utility of the reaction product(the PVA alloy formed in situ) for compatibilization of PVA with LLDPE.

                  TABLE VI                                                        ______________________________________                                        Example 8                                                                               Polyolefin                                                                    Graft                                                               PVA "A"   Copolymer LLDPE      Sepn..sup.1                                                                         MFR.sup.2                                %         %         %          %     g/10 min.                                ______________________________________                                        75        20         5         0     3.9                                      70        20        10         0     1.9                                      65        20        15         0     1.4                                      ______________________________________                                         .sup.1 See Example 6.                                                         .sup.2 ASTM 1238 (Condition L) 230° C., 2160 g.                   

EXAMPLE 9

PVA alloys were prepared by reacting 90, 80 and 70 wt. %, respectively,of PVA "A" described in Example 4 with appropriate amounts of anethylene copolymer (MI=6.5, 14 wt. % vinyl acetate and 0.29 wt. % maleicanhydride) in the presence of 5000 ppm of Irganox 1010 and 500 ppm ofcalcium stearate. The alloys obtained can be extruded into clear films.

EXAMPLE 10

PVA alloys were prepared by reacting 80 and 70 wt. %, respectively, of aPVA with a DP of 500-700, M_(n) =22,000-31,000 and which is 87 molepercent hydrolyzed with the ethylene graft copolymer described inExample 1. The reaction products so obtained are well dispersed withoutmacrophase separation.

EXAMPLE 11

The oxygen permeability of PVA "A", PVA "B", and their alloys asdescribed in Example 3 were measured at room temperature (22°-24° C.)using an "Ox-Tran 100" oxygen permeability measurement device (MoconModern Controls, Inc., Elk River, Minn.) and compared with Mylar® andnylon 6 films according to ASTM D-3985-81. The results are shown belowin Table VII.

                  TABLE VII                                                       ______________________________________                                        Example 11                                                                                      Polyolefin                                                                    Graft                                                       PVA "A" PVA "B"   Copolymer Oxygen Permeability                               %       %         %         (cc-mil/m.sup.2 · 1 da. 1                ______________________________________                                                                    atm)                                              100      0         0        0.3                                               80       0        20        0.36                                              0       100        0        21.3                                              0        80       20        44.1                                              Mylar ® (oriented PET)                                                                        55                                                        Nylon 6             40                                                        ______________________________________                                    

EXAMPLE 12

90 wt. % of PVA "A" described in Example 3 is blended with 10 wt. % of ahigh density polyethylene copolymer (HDPE) with a density of 0.949 g/ccand a high load melt index of 20 under the same conditions as describedin Example 8. At least 7.5% of the material can be distinguished as aseparate macrophase.

EXAMPLE 13

An alloy was prepared in situ by using 80 wt. % of PVA "A", 10% of anethylene-hexene-1 copolymer with a density of 0.949 g/cc and a high loadmelt index (HLMI) of 20 g/10 min, and 10 wt. % of the polyolefin graftcopolymer described in Example 1 under the conditions described inExample 7.

EXAMPLE 14

The HDPE in Example 12 is replaced by low density polyethylenehomopolymer (LDPE) with a density of 0.919 g/cc and an MI of 2.5. Atleast 4 wt. % of the material is observed as a separate macrophase.

EXAMPLE 15

An alloy was prepared in the same manner as described in Example 13except that a branched low density polyethylene with an MI of 2.5 g/10min and a density of 0.919 g/cc was substituted for an ethylenecopolymer.

EXAMPLE 16

An alloy was prepared from 80 wt. % PVA (87 mole % hydrolyzed with a 4%aqueous solution viscosity at 20° C. of 5 cps) and 20 wt. % of anethylene-acrylic acid copolymer (EAA-6.5 wt. % acrylic acid) by mixingin a Brabender mixer at 425° F. for 5 min.

EXAMPLE 17

An alloy was prepared from 85 wt. % of the PVA described in Example 16,10 wt. % of the EAA described in Example 16, and 5 wt. % of the LLDPEdescribed in Example 7 by mixing in a Brabender mixer at 425° F. for 15min.

EXAMPLE 18

An alloy was prepared by mixing in a Brabender mixer at 425° F. for 10minutes 90 wt. % of the PVA described in Example 16 and 10 wt. % of azinc ionomer of ethylene-methacrylic acid in which 10.1 wt. %methacrylic acid is 70% neutralized.

EXAMPLE 19

An alloy was prepared by mixing in a Brabender mixer at 425° F. for 15minutes 80 wt. % of the PVA described in Example 16 and 20 wt. % of theionomer described in Example 18.

EXAMPLE 20

An alloy was prepared by mixing in a Brabender mixer at 425° F. for 5minutes 80 wt. % of the PVA described in Example 16 and 20 wt. % of apolypropylene grafted with 0.23 weight % of maleic anhydride.

EXAMPLE 21

An alloy was prepared similarly to the procedure of Example 20 by using80 wt. % of the PVA described in Example 16, 10 wt. % of the graftedpolypropylene of Example 20 and 10 wt. % of either a block polypropylene(PP) polymer containing 5% ethylene or 10 wt. % of a random PP polymercontaining 1.8% ethylene.

EXAMPLE 22

Similar alloys were prepared by substituting a PVA with a DP of 600 and74 mole % hydrolysis for the PVA of Examples 20 and 21.

EXAMPLE 23

Varying percentages of PVA, as designated in Table VIII, below, and anethylene-propylene (EP) elastomer containing 65 wt. % ethylene with adensity of 0.86 g/cc were blended in an electrically heated scroll mixerat 425° F. (218° C.) for 5 min. at 120 rpm. Two macrophases wereobserved which were different in color and behavior. The smaller portionis indicated as separation percent in Table VIII. These data show thatEP cannot be completely dispersed in PVA.

                  TABLE VIII                                                      ______________________________________                                        Example 23                                                                    PVA "A"   PVA "B"       EP     Separation                                     %         %             %      %                                              ______________________________________                                        90        --            10     7.8                                            --        95             5     3.6                                            --        90            10     6.3                                            --        80            20     15.4                                           ______________________________________                                    

EXAMPLE 24

A number of alloys were prepared using PVA "A" and PVA "B" with an EPgraft copolymer prepared by using an XMNA graft of the EP elastomer ofExample 23 (0.8 wt. % XMNA, 0.04 MI). No separation occurred as shown inTable IX, below.

                  TABLE IX                                                        ______________________________________                                        Example 24                                                                    PVA "A"   PVA "B"      EP graft Separation                                    %         %            %        %                                             ______________________________________                                        90        --           10       0                                             80        --           20       0                                             --        90           10       0                                             --        80           20       0                                             ______________________________________                                    

EXAMPLE 25

85 wt. % PVA "A", 10 wt. % of the EP graft copolymer of Example 24 and 5wt. % of a HDPE with a density of 0.949 and an HLMI of 20 were blendedat 425° F. (218° C.) for 5 min. to yield an alloy.

EXAMPLE 26

In the same manner as described in Example 25, 70 wt. % of PVA "B", 10wt. % of the EP graft copolymer of Example 24, and 10 wt. % of an LLDPEwith a density of 0.918 and an MI of 2 yields an alloy.

All parts and percentages herein are by weight unless otherwiseindicated.

GLOSSARY OF TERMS

Abbreviations used herein to identify chemical ingredients and productcharacteristics include:

DP--degree of polymerization

EP--ethylene-propylene elastomer

EAA--ethylene-acrylic acid copolymer

EVA--ethylene vinyl acetate copolymer

EVOH--ethylene vinyl alcohol copolymer

FTIR--Fourier Transform Infrared Spectroscopy

HDPE--high density polyethylene

HLMI--high load melt index

LLDPE--linear low density polyethylene

MA--maleic anhydride

MFR--melt flow rate

MI--melt index

M_(n) --number average molecular weight

M_(w) --weight average molecular weight

PE--polyethylene

PET--polyethylene terephthalate

PVA--polyvinyl alcohol

XMNA--x-methyl bicyclo(2.2.1)hept-5-ene-2,3-dicarboxylic anhydride

The foregoing detailed description is given for clearness ofunderstanding only, and no unnecessary limitations are to be inferredtherefrom, as variations within the scope of the invention will beobvious to those skilled in the art.

We claim:
 1. A melt processable polymer alloy prepared by the methodcomprising the steps of:(a) providing a polyvinyl alcohol polymer havinga degree of hydrolysis of less than about 90 mole percent and a degreeof polymerization of about 300 to 900, inclusive; (b) providing afunctional polymer comprising a polyolefin or an ethylene-estercopolymer having functional groups reactive with the hydroxyl groups ofsaid polyvinyl alcohol polymer incorporated therein by copolymerization,said functional groups comprising one or more of a carboxylic acid, acarboxylic acid anhydride, a metal salt of a carboxylic acid, or aderivative thereof; and, (c) thereafter reacting said polyvinyl alcoholpolymer with less than a stoichiometric amount of said functionalpolymer to provide a mixture of grafted and ungrafted polyvinyl alcoholpolymers, said grafted polyvinyl alcohol polymer having less than allavailable hydroxyl groups reacted with said functional groups, saidpolyvinyl alcohol polymer comprising at least about 70 weight percent ofsaid mixture.
 2. The alloy of claim 1 wherein said polyvinyl alcoholpolymer is between about 70 and 90 mole percent hydrolyzed prior toreaction with said functional polymer.
 3. The alloy of claim 1 whereinsaid functional polymer is an ethylene-acrylic acid copolymer, anethylene-methacrylic acid copolymer, an ethylene-alkyl acrylate-acrylicacid copolymer, or an ethylene-alkyl methacrylate-methacrylic acidcopolymer.
 4. The alloy of claim 1 wherein said functional polymer isthe partially neutralized salt of an ethylene-acrylic acid copolymer, anethylene-methacrylic acid copolymer, an ethylene-alkyl acrylate-acrylicacid copolymer, or an ethylene-alkyl methacrylate-methacrylic acidcopolymer.
 5. The alloy of claim 1 which additionally contains ablending resin comprising an olefin homopolymer or copolymer compatiblewith said mixture of grafted and ungrafted polyvinyl alcohol polymersmelt blended with said mixture.
 6. The alloy of claim 5 wherein saidalloy comprises between about 99 and 85 weight percent of said mixtureof (c) and, correspondingly, between 1 and 15 weight percent of saidblending resin.
 7. The alloy of claim 1 formed into a gas barrier film,sheet, tube, coating, bottle or profile.
 8. The alloy of claim 5 formedinto a gas barrier film, sheet, tube, coating, bottle or profile.
 9. Anarticle formed of the alloy of claim 1 by one or more methods chosenfrom the group consisting of blown film extrusion, cast film extrusion,extrusion coating, coextrusion, coextrusion coating, injection molding,blow molding, rotomolding, compression molding, profile extrusion, pipeextrusion, and tubing extrusion.
 10. An article formed of the alloy ofclaim 5 by one or more methods chosen from the group consisting of blownfilm extrusion, cast film extrusion, extrusion coating, coextrusion,coextrusion coating, injection molding, blow molding, rotomolding,compression molding, profile extrusion, pipe extrusion, and tubingextrusion.
 11. A method of preparing a melt processable polymer alloycomprising the steps of:(a) providing a polyvinyl alcohol polymer havinga degree of hydrolysis of less than about 90 mole percent and a degreeof polymerization of about 300 to 900, inclusive; (b) providing afunctional polymer comprising a polyolefin or an ethylene-estercopolymer having functional groups reactive with the hydroxyl groups ofsaid polyvinyl alcohol polymer incorporated therein by copolymerization,said functional groups comprising one or more of a carboxylic acid, acarboxylic acid anhydride, a metal salt of a carboxylic acid, or aderivative thereof; and, (c) thereafter reacting said polyvinyl alcoholpolymer with less than a stoichiometric amount of said functionalpolymer to provide a mixture of grafted and ungrafted polyvinyl alcoholpolymers, said grafted polyvinyl alcohol polymer having less than allavailable hydroxyl groups reacted with said functional groups, saidpolyvinyl alcohol polymer comprising at least about 70 weight percent ofsaid mixture.
 12. The method of claim 11 wherein said polyvinyl alcoholpolymer is between about 70 and 90 mole percent hydrolyzed prior toreaction with said functional polymer.
 13. The method of claim 11wherein said functional polymer is an ethylene-acrylic acid copolymer,an ethylene-methacrylic acid copolymer, an ethylene-alkylacrylate-acrylic acid copolymer, or an ethylene-alkylmethacrylate-methacrylic acid copolymer.
 14. The method of claim 11wherein said functional polymer is the partially neutralized salt of anethylene-acrylic acid copolymer, an ethylene-methacrylic acid copolymer,an ethylene-alkyl acrylate-acrylic acid copolymer, or an ethylene-alkylmethacrylate-methacrylic acid copolymer.
 15. The method of claim 11including the additional step of melt blending with said mixture of (c)a blending resin comprising an olefin homopolymer or copolymercompatible with said mixture of grafted and ungrafted polyvinyl alcoholpolymers.
 16. The method of claim 15 wherein said alloy comprisesbetween about 99 and 85 weight percent of said mixture of (c) and,correspondingly, between 1 and 15 weight percent of said blending resin.17. The method of claim 11 wherein said alloy is formed into a gasbarrier film, sheet, tube, coating, bottle or profile.
 18. The method ofclaim 15 wherein said alloy is formed into a gas barrier film, sheet,tube, coating, bottle or profile.
 19. The method of claim 11 whereinsaid alloy is formed into an article by one or more methods chosen fromthe group consisting of blown film extrusion, cast film extrusion,extrusion coating, coextrusion, coextrusion coating, injection molding,blow molding, rotomolding, compression molding, profile extrusion, pipeextrusion, and tubing extrusion.
 20. The method of claim 15 wherein saidalloy is formed into an article by one or more methods chosen from thegroup consisting of blown film extrusion, cast film extrusion, extrusioncoating, coextrusion, coextrusion coating, injection molding, blowmolding, rotomolding, compression molding, profile extrusion, pipeextrusion, and tubing extrusion.